Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: bucio on 21/04/2008 00:03:16
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Hi,
Recently I've heard that the easiest way to sterilize (or maybe quasi-sterilize) surgical/medical tools is to put them into the microwave oven for a few minutes; AFAIR the paper said, that it is a common method in a field clinics in Africa where such machines as autoclaves and so on are often not available. Does this really work? I've always thought that microwaving metal objects is not a good idea. Can I do it with my hobby-lab tools at home without causing any harm?
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Oh, sorry, I didn't notice the "how the body works" part, but anyway... Feel free to move it into the right topic. Sorry again.
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Hi Bucio and welcome to the site.
I agree.....I've always thought putting metal inside a microwave is a no no but lets hope someone comes back with an answer for you.
In the mean time.....because of the specific nature of your question I guess it's Ok to stay in this section.
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My microwave is metal on the inside, and the manual tells me that if I need to heat up water, I should put a metal spoon in the cup. Don't know how that works...never been game enough to try!
Microwaving surgical tools though. Doesn't seem like the best way to sterilise every surface, but I suppose you can only do with what you can get hold of.
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i would imagine that it probably does sterilize the tools quite well... however as someone who put many-a metal object in the microwave growing up, i have to think that it takes quite a toll on those microwaves.
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My microwave is metal on the inside, and the manual tells me that if I need to heat up water, I should put a metal spoon in the cup. Don't know how that works...never been game enough to try!
The problem with metal in microwaves is twofold.
Firstly, metal reflects the microwaves (hence why the inside of the microwave oven is metal), so if you place a bot of metal over a part of what you are cooking, it will mean that whatever is behind the metal piece will not warm up properly (sometimes this is useful, if you want to cook one piece of the meal more than another, but if it is unintended, then it may mean your food does not cook evenly, and some parts may remain uncooked).
The second problem with metal is if it is too thin it may not properly carry the current, and may heat up (thin gold foil on cups may heat up and peal away from the cup), and where there are small gaps in the metal (e.g. the prongs of a fork), it may cause the microwaves to spark between them.
The reason I can imagine to put a metal spoon in a boiling cup of liquid is to deliberately cause it to heat up unevenly. The problem is that a cup of water in a microwave, if it is heated evenly, does not develop convection currents, and so can become superheated (i.e. can heat above the boiling point of the liquid with out actually boiling off). Then, when you take the cup out of the microwave, the slight movement of the cup can cause it to suddenly start to biol in an explosive fashion, and have boiling hot water explode all over you, causing severe scalding. By placing a metal spoon in the water it protects part of the water from the microwaves, so the water is heated unevenly, so it will cause convection currents to form (as the hotter water rises while the cooler, protected, water falls), thus preventing the water from becoming superheated, and so ensuring the water does to explode when it is taken out of the microwave oven.
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makes sense to me.
.....on a slightly related note, if you want a good fireworks show, put a CD that you don't care much about in the microwave for a few seconds.